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Difference between revisions of "cpp/named req/RandomAccessIterator"

From cppreference.com
< cpp‎ | named req
m (Text replace - "{{concept" to "{{named req")
m (named req/core)
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{{cpp/named req/navbar}}
 
{{cpp/named req/navbar}}
  
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A {{tt|RandomAccessIterator}} is a {{named req|BidirectionalIterator}} that can be moved to point to any element in constant time.
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A {{named req|RandomAccessIterator}} is a {{named req|BidirectionalIterator}} that can be moved to point to any element in constant time.
  
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A pointer to an element of an array satisfies all requirements of {{tt|RandomAccessIterator}}
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A pointer to an element of an array satisfies all requirements of {{named req/core|RandomAccessIterator}}
  
 
===Requirements===
 
===Requirements===
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The type {{tt|It}} satisfies {{tt|RandomAccessIterator}} if
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The type {{tt|It}} satisfies {{named req/core|RandomAccessIterator}} if
  
 
* The type {{tt|It}} satisfies {{named req|BidirectionalIterator}}
 
* The type {{tt|It}} satisfies {{named req|BidirectionalIterator}}
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|}
 
|}
  
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The above rules imply that {{tt|RandomAccessIterator}} also implements {{named req|LessThanComparable}}.
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The above rules imply that {{named req/core|RandomAccessIterator}} also implements {{named req|LessThanComparable}}.
  
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A {{tt|mutable RandomAccessIterator}} is a {{tt|RandomAccessIterator}} that additionally satisfies the {{named req|OutputIterator}} requirements.
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A ''mutable'' {{named req/core|RandomAccessIterator}} is a {{named req/core|RandomAccessIterator}} that additionally satisfies the {{named req|OutputIterator}} requirements.
  
 
===See also===
 
===See also===

Revision as of 01:21, 17 June 2018

 
C++
 
C++ named requirements
 

A LegacyRandomAccessIterator is a LegacyBidirectionalIterator that can be moved to point to any element in constant time.

A pointer to an element of an array satisfies all requirements of LegacyRandomAccessIterator

Requirements

The type It satisfies LegacyRandomAccessIterator if

And, given

  • value_type, the type denoted by std::iterator_traits<It>::value_type
  • difference_type, the type denoted by std::iterator_traits<It>::difference_type
  • reference, the type denoted by std::iterator_traits<It>::reference
  • i, a, b, objects of type It or const It
  • r, a value of type It&
  • n, an integer of type difference_type

The following expressions must be valid and have their specified effects

Expression Return type Operational semantics Notes
r += n It& difference_type m = n;

if (m >= 0) while (m--) ++r;
else while (m++) --r;
return r;

  • n can be both positive or negative
  • The complexity is constant (that is, the implementation cannot actually execute the while loop shown in operational semantics)
a + n

n + a

It It temp = a;

return temp += n;

  • n can be both positive or negative
  • a + n == n + a
r -= n It& return r += -n; The absolute value of n must be within the range of representable values of difference_type.
i - n It It temp = i;
return temp -= n;
b - a difference_type return n;

Precondition:

  • there exists a value n of type difference_type such that a+n==b

Postcondition:

  • b == a + (b - a).
i[n] convertible to reference *(i + n)
a < b contextually convertible to bool b - a > 0 Strict total ordering relation:
  • !(a < a)
  • if a < b then !(b < a)
  • if a < b and b < c then a < c
  • a < b or b < a or a == b
    (exactly one of the expressions is true)
a > b contextually convertible to bool b < a Total ordering relation opposite to a < b
a >= b contextually convertible to bool !(a < b)
a <= b contextually convertible to bool !(a > b)

The above rules imply that LegacyRandomAccessIterator also implements LessThanComparable.

A mutable LegacyRandomAccessIterator is a LegacyRandomAccessIterator that additionally satisfies the LegacyOutputIterator requirements.

See also

 specifies that a BidirectionalIterator is a random-access iterator, supporting advancement in constant time and subscripting
(concept) [edit]
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